Field of the Invention
The present invention relates generally to a light modulation element unit used for an image projection apparatus (projector), and more particularly to a structure for preventing a foreign matter from adhering to the light modulation element.
Description of the Related Art
A projector uses a light modulation element, such as a liquid crystal panel, configured to modulate light from a light source, and can project and display an image onto a target plane, such as a screen. When foreign matters, such as dust floating in cooling air taken in a housing from the outside of the projector, adhere to a modulating plane (such as a cover glass surface) of the light modulation element, the quality of the projected image may deteriorate under influence of the foreign matters.
Japanese Patent Laid-Open No. (“JP”) 11-305674 discloses a dustproof structure that arranges a first dustproof member between a base for holding the light modulation element and a light shield plate that shields light from the light source from entering a modulation area of the light modulation element, and a second dustproof member between the light shield plate and a waveplate which light toward the modulation area passes. JP 2004-020603 discloses a dustproof structure that includes a dustproof cover between a light shield plate on a light modulation element and a polarization beam splitter configured to lead light from the light source to the light modulation element.
The dustproof structures disclosed in JPs 11-305674 and 2004-020603 close the space for the light modulation element but is not sufficient because micro foreign particles can intrude from micro apertures among components in the dustproof structure and put on the modulating plane of the light modulation element.